Currently, as continuous updates of an optical fiber communication system from 100 Gbits/s to 400 Gbits/s or higher transmission rate of a single channel, an intra-channel nonlinear effect in an optical fiber transmission link has become one of important damages affecting the system performance. The key to the study of influence on an effect of nonlinear to the system performance resides in how to quantitatively describe and estimate signal distortion resulted from the effect of nonlinear, so as to provide basis for alleviating or compensating for nonlinear damage.
A basis for the study of an effect of nonlinear in an optical fiber transmission link is a nonlinear equation, which describes an evolution of an optical pulse during transmission. However, as the nonlinear equation is a nonlinear partial differential equation, such a kind of equation usually has no analytic solution. At present, a numerical method that has been widely used is a split-step Fourier (SSF) method, in which a problem of high complexity of calculation exists, resulting in an algorithm of back propagation (BP) digital signal processing of nonlinear damage compensation based on such a method is hard to be carried out. Although an approximation analytic method based on a perturbation theory has an advantage of low complexity, a perturbation model used in an existing method is based on an assumption of a lossless large dispersion link, the analysis and estimation of which on intra-channel nonlinear damage being limited to an optical fiber transmission link without dispersion compensation, and being inapplicable to a current typical dispersion compensation link. FIG. 1 is a schematic diagram of similarity of additive nonlinear noise time-domain waveforms estimated by using the perturbation model and the SSF method at different dispersion compensation rates. As shown in FIG. 1, a value of the similarity is lowered as the increase of the dispersion compensation rate, that is, the similarity of the waveforms of the perturbation model and the SSF method is lowered gradually when the dispersion compensation rate is increased gradually. FIG. 2 is a schematic diagram of comparison of additive nonlinear noise power estimated by using the perturbation model and the SSF method at different dispersion compensation rates. As shown in FIG. 2, the nonlinear damage in a link having dispersion compensation estimated by the perturbation model is invalid.
It should be noted that the above description of the background art is merely provided for clear and complete explanation of the present invention and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background art of the present invention.